spruce and hemlock, to grow under light-demanding trees like the
pine. This system presents a "two-storied" forest and is known by
that name. The under story often has to be established by planting.

[Illustration: FIG. 131.--Diagrammatic Illustration of the Group or
Strip System.]

In the system of reproducing forests from shoots or suckers, all
trees of a certain species on a given area are cut off and the old
stumps and roots are depended upon to produce a new set of sprouts,
the strongest of which will later develop into trees. The coniferous
trees do not lend themselves at all to this system of treatment,
and, among the broadleaf trees, the species vary in their ability to
sprout. Some, like the chestnut and poplar, sprout profusely; others
sprout very little.

How forests are protected: Forestry also tries to protect the forests
from many destructive agencies. Wasteful lumbering and fire are the
worst enemies of the forest. Fungi, insects, grazing, wind, snow and
floods are the other enemies.

[Illustration: FIG. 132.--The Result of a Forest Fire. The trees,
lodgepole pine and Englemann spruce, are all dead and down. Photograph
taken in the Colorado National Forest, Colorado.]

By wasteful lumbering is meant that the forest is cut with no regard
for the future and with considerable waste in the utilization of the
product. Conservative lumbering, which is the term used by foresters
to designate the opposite of wasteful lumbering, will be described
more fully later in this study.